Footage showed flames and smoke flowing from the historic structure, and its spire was engulfed before collapsing.

Construction began on the Gothic cathedral in 1163, and it took over 100 years to complete. Twelve million people stop by each year; it is the most-visited monument in France.

The church's site is full of symbolic decorations, colorful glass, art and gargoyles. The cause of the fire was not immediately known, but officials said late Monday that the church’s main structure had been saved after firefighters prevented the flames from spreading to the northern belfry.

Notre Dame Cathedral is burning in Paris on Monday, April 15, 2019. Massive plumes of yellow brown smoke is filling the air above Notre Dame Cathedral and ash is falling on tourists and others around the island that marks the center of Paris. AP

Notre Dame cathedral is burning in Paris, April 15, 2019. Massive plumes of yellow brown smoke is filling the air above Notre Dame Cathedral and ash is falling on tourists and others around the island that marks the center of Paris. Lori Hinant, AP

According to the Napoleon Foundation, the cathedral was renamed "Temple to the Goddess Reason" and at one point served as a storage place for wine.

When France and the Catholic Church reconciled in 1801, the cathedral was returned to the church. Napoleon later used it during his coronation, according to the foundation.

The Hunchback of Notre Dame

Victor Hugo's novel "The Hunchback of Notre Dame," published in 1831, centers on Quasimodo, the cathedral's bell-ringer, and Esmeralda, a kind and beautiful street dancer.

The novel has been adapted into a number of films, including the popular animated Disney version "The Hunchback of Notre Dame" in 1996.

It was home to relics tied to the Passion of Jesus

The cathedral's "most precious and most revered object" is the Crown of Thorns, according to France's tourism website. Before Jesus was crucified, Roman soldiers mocked him and stuck a crown made of thorns on his head. However, around the world, others claim to have portions of the crown or single thorns.

A priest wipes the Crown of Thorns, a relic of the passion of Christ at Notre Dame in Paris on April 14, 2017.(Photo: PHILIPPE LOPEZ, AFP/Getty Images)

Other important relics in the cathedral include a fragment of the True Cross, believed to be part of the cross on which Jesus was crucified, and one of the Holy Nails, believed to be used in the crucifixion.

In addition to religious relics, masterpiece artworks and sculptures, stained-glass windows and three organs are also housed at Notre Dame, its website says.

Salvage efforts had been underway to recover precious artifacts, and city prosecutors announced they were opening an investigation.

"A special mission has been launched to try to save all works of art that can be saved," Emmanuel Grégoire, first deputy to the mayor of Paris, said on French TV.